The titular character, a RobotKid created by [[GadgeteerGenius Professor Moshimo]] with [[BadassAdorable the most advanced fighting capabilities on the planet]]...[[NaiveNewcomer and the mentality of an 11-year old Japanese exchange student.]] To keep certain less savory personalities from using him for [[TakeOverTheWorld the wrong purposes,]] Moshimo sends him to live with Tommy Turnbull, where he learns to become a real boy.

* AnIcePerson: Gets a freeze ray in "The Boy Who Cried Kamikazi!"* BadassAdorable* BecomeARealBoy* BrainwashedAndCrazy: In "Crying Time"* CainAndAbel: With Protoboy.* TheCassandra: Tommy wouldn't believe him about [[PreciousPuppies Sparky]] being evil in "Dog-Ra". Oops.** CassandraDidIt: ...Leading to him being blamed for destroying the house when he was trying to defend himself from Sparky in humongous-robot-form. * CheerfulChild* ConstantlyCurious* {{Expy}}: His design, background, and color scheme calls to mind two other robot boys of Japanese origin: Anime/AstroBoy and [[VideoGame/MegaManClassic Mega Man]].* FlyingBrick: Hoooooo boy. If we tried to list all his powers starting from episode one, we'd be here all day and then some. [[{{Seer}} Probability calculator,]] [[AnIcePerson freeze ray,]] [[MoreDakka bullets,]] [[GoodOldFisticuffs kung-fu skills,]] [[{{Flight}} rocket boosters,]] [[FrickinLaserBeams laser beam,]] [[PlayingWithFire flamethrower]]...* NiceJobBreakingItHero: Reactivating Protoboy in "Brother".* TheNoseless* PintsizedPowerhouse* RedEyesTakeWarning* SleepModeSize: Can pass off as an action figure while in sleep mode.* SuperStrength* TalkingtoHimself: With Lola.* TelescopingRobot: He gets bigger during his [[SuperMode super activation]].* YouNoTakeCandle: He alongside Moshimo's other robots speak like this.

->''"Professor Moshimo must be in some kind of trouble! Maybe Robotgirl can help us!"''

->Voiced by: Lorraine Pilkington

The other co-protagonist of the show, a fairly average young boy who was chosen by Moshimo to take care of Robotboy and be his teacher of sorts. He has a very good knowledge of robotics and often plays the StraightMan to Gus.

* {{Adorkable}}* AllLoveIsUnrequited: His crush on Bambi. * AlliterativeName* ArchEnemy: Kurt* {{Deuteragonist}}* DistressedDude: A fair few times.* MentorArchetype * RedOniBlueOni: Blue to Gus's red.* SatelliteCharacter: If you think about it. He exists for Lola and Gus to have a third friend, Robotboy to have a best friend, Kurt and Donnie to make fun of, and...that's it.* ShesAManInJapan: He is female in the the Chinese, Korean, Japanese, Vietnamese, Mongolian, Kazakh and Kyrgyz dubs.* TheUnfavorite: At least as far as his dad is concerned.* VitriolicBestBuds: With Gus.* WideEyesAndShrunkenIrises: In "Valentine's Day" when he sees Bambi walk by.[[/folder]]

Another friend of Tommy and Robotboy, and was friends with Tommy and Lola even before Robotboy came along. Much less heroic than his friends, but still a good guy at heart.

* AbhorrentAdmirer: To Lola.* AntiHero: Almost a NominalHero at times.* BigEater* BigFun[=/=]FatIdiot: [[DependingOnTheWriter Depending on the episode.]]* BookDumb* BroughtToYouByTheLetterS: The stylized "G" on his shirt.* ButtMonkey* CasanovaWannabe: Tries to hit on Lola many times, only to be shot down every time.* {{Expy}}: He's essentially a [[LighterAndSofter G-rated]] [[WesternAnimation/SouthPark Eric Cartman]]. * ExtremeOmnivore-->'''Gus:''' Haha! I ate all your candy!-->'''Tommy:''' That was soap.-->'''Gus:''' Huh? ...Haha! I ate all your soap!* FatBestFriend: To Tommy.* {{Jerkass}}/{{Jerk With A Heart Of Gold}}: He's smug, stupid, full of himself, and sometimes is even the reason that episodes have conflicts, but he'll always be there to be with Tommy and the others when they need him.* NakedPeopleAreFunny: In "Halloween" and at the end of "Tummy Trouble".* OnlyOneName** His last name, although it's not used often, is [[ShoutOut Bachman-Turner]]* RedOniBlueOni: Red to Tommy's blue.* ShipperOnDeck: For Tommy/Lola, although it's more that he likes to tease them about it than anything.* TemporaryBulkChange: The tapeworm in "Tummy Trouble" makes him thin instead of fat.* TokenEvilTeammate* VocalEvolution: In earlier episodes, his voice was lower-pitched.

The fourth and last member of Tommy's TrueCompanions and the only girl, as well as the daughter of a famous ambassador.

* BettyAndVeronica: Betty to Bambi's Veronica.* CloserToEarth* DistressedDamsel: Near the end of "The Manchurian Robot" and "Valentine's Day".* MagicSkirt* NiceGirl* PositiveDiscrimination* SmoochOfVictory: Gives one to Tommy at the end of "Valentine's Day"* SmurfettePrinciple* SpoiledSweet* TokenMinority* {{Tsundere}}: Type B, as she's generally nice but can get violent (particularly with Gus) or cold if pushed.[[/folder]]

[[folder:Professor Moshimo]]

->''"How do you like my new house? Undetectable by radar, and safe from Dr. Kamikazi."''

->Voiced by: Togo Igawa

The scientist who invented Robotboy, as well as Robotgirl and Protoboy. He keeps in touch with Tommy, Gus and Lola to send upgrades for Robotboy or help them fix the problem of the day.

->''"He's not Ro anymore! He's a finely tuned killer robot...who does exactly what I say. And I say...GET HIM!"''

->Voiced by: Eiji Kusuhara

The main antagonist of the show, an evil scientist who wants to steal/kidnap Robotboy and make an army of Robotboy clones to take over the world.

* AnimalsHateHim: Every time he gets a pet. Every. Single. Time.* AwLookTheyReallyDoLoveEachOther: In "Bad Language" he screams and faints when Constantine is about to fall into a volcano.* BadBoss* BigBad: As if we needed to say it.* CardCarryingVillain: Kamikaze on numerous occasions has proclaimed his title as an evil genius.* EvilOldFolks* FailureIsTheOnlyOption* KavorkaMan: Despite being a short, creepy, and bespectacled old man, he manages to attract statuesque and beautiful women quite easily.* KickTheDog: Pretty much describes his entire relationship with Constantine.* JerkWithAHeartOfJerk: In "Teasebots".* LargeHam* MadScientist: "Frozen sea monkeys, ATTAAAAAAACK!"* MiniatureSeniorCitizens* MorallyAmbiguousDoctorate: According to his mother, he's not a real doctor.* PetTheDog: He has attempted this countless times with his various pets. It never works.

[[/folder]]

[[folder:Constantine]]

->''"Ah, boss, I'd be happier if you'd have some milk."''

->Voiced by: Rupert Degas

Kamikazi's ever-loyal sidekick.

* {{Acrofatic}}: He displays quick reflexes and amazing agility for someone with such a portly figure.* AffablyEvil* AntiVillain* ButtMonkey: Being abused by Kamikazi in every possible way has got to count for something.** TheChewToy* CampStraight* CrouchingMoronHiddenBadass: He is quite skilled despite his often goofy behavior. He was the who defeated Protoboy after he went berserk from being turned pure evil.* TheDragon* PetTheDog: He tried to save Salvatorei the gerbil from being made into Kamikazi's soup in "Teasebots".* SupremeChef* WhyDidItHaveToBeSnakes: "Oh, shut your trap, boss! That snake gives me the heebie-jeebies!"

[[/folder]]

[[folder:Protoboy]]

->''"Protoboy no so easy to destroy! And now get revenge on brother!"''

Moshimo's first robot and Robotboy's big brother, he was turned evil by Kamikazi, but turned out to be too insane to control and had to be deactivated.

* AxCrazy: Dear ''God.''* BigBrotherBully* CainAndAbel* EvenEvilHasLovedOnes: A one-off gag in "The Revenge of Protoboy", when a call from his wife stops him from destroying Robotboy at the last second.* EvilCounterpart: To Robotboy* {{Expy}}: Has the background of [[VideoGame/MegaManClassic Proto Man]] but a more similar personality and design to Bass from the same franchise.* FaceMonsterTurn* GoneHorriblyRight: Kamikazi intended to make him evil...and overdid it.* GrandTheftMe: Trades motherboards with a fainted Robotboy in "The Old Switcharobot".* JacobMarleyWarning: In a sense.* PsychoPrototype* TheSociopath* WouldHitAGirl: "The Return of Robotgirl"

[[/folder]]

[[folder:Robotgirl]]

->''"We have fun. Play now. Yes, please?"''

->Voiced by: Laurence Bouvard

A female clone of Robotboy created to keep him company at Moshimo's house when Tommy had to leave for a two-week camping trip.

* BadassAdorable / CuteBruiser: Averted in "Robotgirl" where she doesn't know how to fight, but played straight in "The Return of Robotgirl". * BreakTheCutie: Right before "The Return of Robotgirl".* CainAndAbelAndSeth* CheerfulChild* DistaffCounterpart* {{Expy}}: Of [[VideoGame/MegaManClassic Roll]], arguably.* FanficMagnet: She's only in two episodes, but gets a lot of fan art and {{YouTube}} videos.* FemBot* GenkiGirl: Subverted in "The Return of Robotgirl" when she is shown to be very sad and doesn't trust Tommy, Gus or even Robotboy due to choppy MEMORY LOSS.* PaletteSwap* PinkMeansFeminine: Her bow, gloves, skirt, eyes, boots and "ears".* RedEyesTakeWarning* TechnicolorEyes: Well, she ''is'' a robot...* ZettaiRyouiki: Grade B/C.

[[/folder]]

[[folder:Donnie Turnbull]]

->''"Someones getting a beatdown."''

->Voiced by: Rupert Degas.

The Older Brother of Tommy who bullys other people (with the Exception of Debbie, Dwight who are his parents, and Kurt, and other Villains.)

* BigBrotherBully: To Tommy Turnbull* BigOlUnibrow* DeathGlare* DemotedToExtra: He is rarely seen in Season 4.* {{Jerkass}}* OutOfFocus: He appears the most in Season 1.[[/folder]]